nǐ yùdìng le shénme fángxíng?

了 marks the action as completed or realized. In this sentence, it shows that the booking has already been made.

So 你预订了什么房型？ means something like:

• You booked what type of room?
• What room type did you book?

It is not simply a past-tense marker like English -ed. It is an aspect marker, so it focuses on the action being completed.

Without 了, the meaning changes. For example:

• 你预订什么房型？ can sound incomplete or unnatural in many contexts.
• 你要预订什么房型？ means What room type do you want to book?

In Chinese, question words usually stay in the same place where the answer would go. This is very different from English.

Statement:

• 你预订了大床房。
• You booked a double room / queen room.

Question:

• 你预订了什么房型？
• You booked what room type?

So Chinese does not usually move 什么 to the front the way English moves what.

This is a very important pattern:

• 你吃了什么？
• 他买了什么？
• 你预订了什么房型？

什么房型 means what kind of room type or which room category.

Here, 什么 is modifying the noun 房型. So the structure is:

• 什么 + noun
• what + noun

Examples:

• 什么时间 = what time
• 什么地方 = what place
• 什么房型 = what room type

So this is not two separate ideas. It is one noun phrase: 什么房型.

Not exactly.

房型 refers to the type or category of room, such as:

• single room
• double room
• twin room
• suite
• sea-view room

房间 means room in a more general sense, as a physical room.

So:

• 房型 = room type
• 房间 = room

If a hotel worker asks 你预订了什么房型？, they are asking about the category of room, not the room number or the room itself.

Both can mean to book or to reserve, but 预订 is a bit more formal and more explicit about reserving in advance.

• 订 = to book/order/reserve
• 预订 = to reserve in advance; often more formal

In hotel, travel, and ticket contexts, both are common, but 预订 sounds especially appropriate in formal service language.

So these are both natural:

• 你订了什么房型？
• 你预订了什么房型？

The second one sounds a little more formal or polished.

Yes, and in many real hotel situations, 您 would be more polite.

• 你预订了什么房型？ = What room type did you book?
• 您预订了什么房型？ = same meaning, but polite/respectful

If a hotel receptionist is speaking to a guest, 您 is often more appropriate.

So in real life, you may hear:

• 您预订了什么房型？

Because in Chinese, modifiers come before the noun.

Since 什么 is modifying 房型, it must come before it:

• 什么房型 = what room type

You cannot say:

• 房型什么

That word order does not work in standard Chinese.

This is the same pattern as:

• 什么人 = what person / what kind of person
• 什么东西 = what thing
• 什么问题 = what question / what problem

Yes. 哪种房型 is also very natural.

There is a slight nuance:

• 什么房型 = what room type
• 哪种房型 = which kind of room type

哪种 can sound a little more specific, especially when choosing among known categories.
什么 is broader and very common in everyday speech.

So all of these can work, depending on context:

• 你预订了什么房型？
• 您预订了哪种房型？

Both are correct and natural.

Sometimes, but not if you want to keep the exact meaning of this sentence.

With 了, the sentence asks about a booking that has already been completed:

• 你预订了什么房型？

If you remove 了, the sentence may sound less natural by itself, or the time reference becomes less clear:

• 你预订什么房型？

To ask about a future choice, Chinese usually adds another word, such as:

• 你要预订什么房型？ = What room type do you want to book?
• 你想预订什么房型？ = What room type would you like to book?

So 了 is important here because it matches the idea of an already-made reservation.

Because 房型 is being asked about as a category, not counted as an individual item.

Chinese often uses measure words with numbers or demonstratives, for example:

• 一种房型 = one type of room
• 哪一种房型 = which type of room

But in 什么房型, no measure word is needed. This is a very normal pattern.

You could say:

• 什么房型
• 哪种房型
• 哪一种房型

All are grammatical, but they have slightly different styles.
什么房型 is concise and natural.

It is pronounced shénme.

A few useful points:

• 什 is second tone: shén
• 么 is usually pronounced with a neutral tone: me

So learners should usually say:

• shénme

not a fully stressed shénmó.

In natural speech, the second syllable is light and unstressed.

The pattern is:

• Subject + Verb + 了 + Question word + Object noun

In this sentence:

• 你 = subject
• 预订 = verb
• 了 = completed-action marker
• 什么房型 = object phrase

So the full structure is:

• 你 + 预订 + 了 + 什么房型？

A useful way to understand it is to first imagine the statement:

• 你预订了大床房。

Then replace the specific room type with a question word:

• 你预订了什么房型？

That is a very common way Chinese questions are formed.